be doing a land-office business

be doing a land-office business

or

be doing land-office business

AMERICAN, OLD-FASHIONED
If a company is doing a land-office business or is doing land-office business, it is very successful. The Paradiso, one of the capital's newest and most luxurious clubs, was doing a land-office business. Scooter and bicycle dealers are doing land-office business. Note: In the United States before the Civil War, the government opened up land offices which sold rights to pieces of land in the West. So many people wanted to buy land to settle on that there were often long queues outside the offices before they opened in the morning.
See also: business